Characterization of pre-cross-connected trails for optical mesh network protection

Recently there has been interest in so-called pre-cross-connected protection architectures for optical networks. The main benefit of pre-cross-connected protection is that multiple cross-connection actions are not required in real time at the time of failure. This addresses the practical concern that, in a transparent optical network, one may not be able to make a series of protection path-forming cross-connections in a succession of optical spans with certainty that the resultant end-to-end connection has optical path integrity. Self-healing rings, p-cycles, and preconnected linear segment protection are examples of prior methods that employ prefailure cross-connection of protection capacity but are not end-to-end path-oriented. More recent work has proposed pre-cross-connected trails (PXTs), which are fully preconnected linear path-protecting structures. The same work also provided an online heuristic algorithm for generating PXT network designs. However, important and interesting properties such as length and cyclicity of the PXT structures remained to be characterized. We delve further into PXT network design, attempting to validate claims made previously and to understand the structural and operational properties of PXTs. This involves reimplementation of and experimentation with the above heuristic. Results show that heuristically obtained designs frequently contain PXTs of great total length and high complexity, as well as other PXTs that are equivalent to 1+1 automatic protection switching (APS) arrangements. Through diagramming and statistical analysis of PXT characteristics we give the first intuitive appreciation of the structure and function of PXTs.